The Gulf of Mexico is a huge ecosystem. With 600,000 square miles and an average depth of 6,000 feet, there is a lot of blue out there for fish to find a home. But oddly enough, 69% of the species found in the northern Gulf live on the bottom – known as benthic fish. This makes sense really. In the open blue, there are few places to hide from predators. On the other hand, the seafloor has numerous places to help avoid being prey. Some make short migrations into estuaries for breeding, but long open ocean migrations are not common.
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Speckled Trout © Jay Fleming
Most benthic fish have a general body design for their environment. They are generally deep bodied, more rounded – as are their fins. They have a higher percentage of “white muscle” which makes them very explosive swimmers – for a few seconds. This is how they live. Blending in with the bottom, they wait for their prey to get within range and then explode on it. This “white muscle” also gives benthic fish a distinctive taste, different from the “red muscle” typically found in the open water fish.
The sense of smell is an important adaptation for finding food. Many have taste and smell buds extended on fleshy appendages called barbels (“whiskers”) and their mouths on the bottom side of their head for easier eating.
Red Drum aka Redfish
There are actually two types of flatfish in the world’s seas – both represented in the Gulf: the Flounder and the Sole. They are born as a typical, normal looking fish, but as they grow one eye begins to “slide” across the top of the head to the other side, winding up with both eyes on one side of the head. In our part of the Gulf, if the eyes slide to the left side – we call it a flounder, to the right it’s a sole. Once the eyes have moved, the fish lose color on the other side and is a flatfish. They can bury in sand and wait for prey. Most species have chromatophores in their skin. These are cells that allow them to change color, like a chameleon or octopus. So, they can change their color to blend into whatever bottom type they are on.
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There is a reason for this adaptation. If your eyes were placed on each side of a torpedo pointed head, you would have what we call monocular vision. This type of vision gives you ALMOST 360° range of view… almost. So even though you can see what is behind you while facing forward, you do not have good depth perception – so you are not sure exactly how far away anything is. You must either rely on other senses to help you out, or get lucky. Having both eyes on one side (or in front like humans), results in binocular vision. You cannot see behind you, but you can tell the distance of the object in front of you. This is beneficial for a predator fish like flounder, who pretty much just lays in wait for its next meal.
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Flounder © Carol Cox
Drums are the largest family of fish in the northern Gulf of Mexico – with 18 species described. The whiting, kingfish, croakers, trout, some perch, and others all belong to this group. They are popular with fishermen and seafood consumers. The Red Drum, also known as Redfish, is one of the more popular targets in our area. Speckled Trout, also called Spotted Sea Trout, are also a favorite. Most have the characteristic body of a benthic fish: deep bodied, rounded fins, mouth on the bottom. Sea trout have two large Dracula looking fangs for grabbing shrimp and other prey. In most, one has broken off and the angler usually finds only one fang present. Some species, such as the Black Drum, have short “whiskers” on their chins used for finding food.
Their common name drum (or croaker) comes from the sounds they produce using their swim bladders. Swim bladders are large sacs within many fish they can fill with gas to float off the bottom. The drum-croaker group rubs this sac with internal muscles making resonating sounds that sound like they are croaking. Atlantic bottlenose dolphin can hear this as well, and croakers make up a big part of their diet.
The eating habits and feeding range of the Red Drum (Redfish) change as they mature. At about four years, they become more of an offshore than inshore fish. They will often travel in schools and feed on shoaling bait like Mullet and Menhaden. Redfish push their prey to the top and have a “feeding frenzy” that attracts other predators, such as birds and sharks, that are also looking for a feast.
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There are 16 species of eels in the northern Gulf. With the exception of the morays – eels live in sandy or muddy bottoms. The American Eel has a unique life history. They spawn in the middle of the Atlantic Ocean, a place known to the sailors as the Sargasso Sea. It is in the middle of the vortex of ocean currents. The young that catch the northern currents and head to Europe are known as the European Eel. Those that catch the southern swirl end up here in the United States are known as the American Eel. Their young look like thin pieces of plastic with eyes. Known as elvers, they can be found within Pensacola Bay by the thousands when they arrive. The growing adults move upstream and spend part of their lives in our rivers and springs, before swimming back to the Atlantic and starting the process all over.
Heron Capturing an American Eel
Marine Catfish are oily and not as popular as their freshwater cousins as food, but they have a strange story associated with them. The skull of the sea catfish is very hard and the bones on the belly side are said to resemble the crucifix. The fish skull is sold in some novelty stores as the crucifix fish. To add to the legend, when you shake the skull, it rattles. This has been described as “soldiers rolling dice” at the crucifixion. They are actually loose bones. Hardhead Catfish are pretty common. The long barbels are for finding food buried beneath the sand or mud. It is also believed they provide a form of echolocation to detect prey. The saltwater catfish has another unique adaptation. The males carry the developing eggs within their mouths. Development takes about two weeks and young fish emerge from dad ready for the world.